Such measuring instruments, which will be interchangeably referred to herein as drying balances, are known from the European patent EP 2 574 900 A1.
Expressed in simple terms, a drying balance is a balance that is connected to a closed, heatable weighing chamber, in which the sample to be weighed can be positioned on a weighing pan, which is connected to a weighing device by way of a load receiver and can be heated by a heating device until the moisture contained in the sample to be weighed has at least partially escaped. The amount of weight that the sample to be weighed loses due to the moisture loss is recorded by the weighing device, so that the recorded weight profile can be used to draw conclusions about the moisture relevant properties of the sample to be weighed. The latter typically takes place in an electronic control unit, which is connected to the weighing device and which is also used to drive the electronic power unit, which supplies the heating element with the requisite operating voltage. The heating element itself can be implemented, for example, as a heating rod that radiates infrared radiation, as a microwave radiator or in any other way.
The aforementioned, generic publication discloses a base, which comprises an outer housing, in which both the weighing device as well as the control unit and the electronic power unit are included. The upper surface of the housing is configured in a stepped manner and forms both the weighing chamber floor as well as the rearward weighing chamber wall that faces away from the ordinary user. This rearward wall of the weighing chamber is horizontally traversed by a load arm, which functions as a weighing pan support and forms the mechanical connection between the weighing pan, disposed in the weighing chamber, and the weighing device, disposed inside the housing. Pivotally connected to the housing is a hood, which forms the two side walls and the front wall of the weighing chamber as well as a lid of the weighing chamber and contains the heating element below the lid of the weighing chamber. In the closed state of the hood the heating element makes contact with a contact point of the base, which is electrically connected to the electronic power unit in the interior of the housing. In order to open the hood, the hood can be pivoted into its open position, so that the weighing plan is accessible for loading with a sample to be weighed. The drawback with the known device is that the weighing chamber is difficult to clean. Especially in the case of drying balances not only pure water, but also other fluids, which can condense on the walls of the weighing chamber and can form deposits, which are difficult to remove, evaporate as a function of the specific sample to be weighed. This evaporation is not just a visual problem; rather there is the risk that subsequent loads of the sample to be weighed will be contaminated. The problem is made worse by the heating element, which is disposed in the hood and through which the deposits can be permanently burned into the material, of which the wall is made.